# std::experimental::filesystem::is_block_file

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< cpp‎ | experimental‎ | fs

Defined in header `<experimental/filesystem>` |  |
bool is_block_file( file_status s ); | (1) | (filesystem TS)
bool is_block_file( const path& p ); bool is_block_file( const path& p, error_code& ec ) noexcept; | (2) | (filesystem TS)

Checks if the given file status or path corresponds to a block special file, as if determined by the POSIX S_ISBLK . Examples of block special files are block devices such as /dev/sda or /dev/loop0 on Linux.

1) Equivalent to s.type() == file_type::block.
2) Equivalent to is_block_file(status(p)) or is_block_file(status(p, ec)).

### Parameters

s | - | file status to check
p | - | path to examine
ec | - | out-parameter for error reporting in the non-throwing overload

### Return value

true if the file indicated by p or if the type indicated s refers to a block device. The non-throwing overload returns false if an error occurs.

### Exceptions

1)
`noexcept` specification:
noexcept
2) The overload that does not take an error_code& parameter throws filesystem_error on underlying OS API errors, constructed with p as the first argument and the OS error code as the error code argument. std::bad_alloc may be thrown if memory allocation fails. The overload taking an error_code& parameter sets it to the OS API error code if an OS API call fails, and executes ec.clear() if no errors occur. This overload has
`noexcept` specification:
noexcept

### Notes

The information provided by this function is usually also provided as a byproduct of directory iteration. During directory iteration, calling `is_block_file(*iterator)` is less efficient than `is_block_file(iterator->status())`.

### Example

Run this code

    #include <cstdio>
    #include <cstring>
    #include <experimental/filesystem>
    #include <fstream>
    #include <iostream>
    #include <sys/socket.h>
    #include <sys/stat.h>
    #include <sys/un.h>
    #include <unistd.h>

    namespace fs = std::experimental::filesystem;

    void demo_status(const fs::path& p, fs::file_status s)
    {
        std::cout << p;
        // alternative: switch(s.type()) { case fs::file_type::regular: ... }
        if (fs::is_regular_file(s))
            std::cout << " is a regular file\n";
        if (fs::is_directory(s))
            std::cout << " is a directory\n";
        if (fs::is_block_file(s))
            std::cout << " is a block device\n";
        if (fs::is_character_file(s))
            std::cout << " is a character device\n";
        if (fs::is_fifo(s))
            std::cout << " is a named IPC pipe\n";
        if (fs::is_socket(s))
            std::cout << " is a named IPC socket\n";
        if (fs::is_symlink(s))
            std::cout << " is a symlink\n";
        if (!fs::exists(s))
            std::cout << " does not exist\n";
    }

    int main()
    {
        // create files of different kinds
        fs::create_directory("sandbox");
        std::ofstream("sandbox/file"); // create regular file
        fs::create_directory("sandbox/dir");
        mkfifo("sandbox/pipe", 0644);
        struct sockaddr_un addr;
        addr.sun_family = AF_UNIX;
        std::strcpy(addr.sun_path, "sandbox/sock");
        int fd = socket(PF_UNIX, SOCK_STREAM, 0);
        bind(fd, (struct sockaddr*)&addr, sizeof addr);
        fs::create_symlink("file", "sandbox/symlink");

        // demo different status accessors
        for (auto it = fs::directory_iterator("sandbox"); it != fs::directory_iterator(); ++it)
            demo_status(*it, it->symlink_status()); // use cached status from directory entry
        demo_status("dev/null", fs::status("/dev/null")); // direct calls to status
        demo_status("dev/sda", fs::status("/dev/sda"));
        demo_status("sandbox/no", fs::status("/sandbox/no"));

        // cleanup
        close(fd);
        fs::remove_all("sandbox");
    }

Possible output:

    "sandbox/file" is a regular file
    "sandbox/dir" is a directory
    "sandbox/pipe" is a named IPC pipe
    "sandbox/sock" is a named IPC socket
    "sandbox/symlink" is a symlink
    "dev/null" is a character device
    "dev/sda" is a block device
    "sandbox/no" does not exist

### See also

statussymlink_status | determines file attributes determines file attributes, checking the symlink target (function)
file_status | represents file type and permissions (class)
status_known | checks whether file status is known (function)
is_character_file | checks whether the given path refers to a character device (function)
is_directory | checks whether the given path refers to a directory (function)
is_fifo | checks whether the given path refers to a named pipe (function)
is_other | checks whether the argument refers to an other file (function)
is_regular_file | checks whether the argument refers to a regular file (function)
is_socket | checks whether the argument refers to a named IPC socket (function)
is_symlink | checks whether the argument refers to a symbolic link (function)
exists | checks whether path refers to existing file system object (function)
statussymlink_status | cached status of the file designated by this directory entry cached symlink_status of the file designated by this directory entry (public member function of `std::experimental::filesystem::directory_entry`)

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